There have been an imaging device, such as a digital camera, which can be connected to a microscope so as to measure a distance between two points on the photographed digital image. In the case of such a conventional imaging device, however, only a distance between two points existing in a same photographic field of view (hereafter also called “photographing range”) can be measured, therefore a dedicated apparatus, such as a measuring microscope and a range finder, is used for measuring a distance between two points that are not within one photographing range (e.g. see Patent Document 1).    [Patent Document 1] Patent No. 3652014
Such a dedicated apparatus, however, is expensive, and a simple means for measuring a distance between two points that are not within one photographing range is demanded for a microscope other than a measuring microscope.